To check the validity of this conclusion in THz scenarios, the system capacity versus SNR is simulated in Fig. REF  for three channels types: Gaussian (zero mean and unit variance; typical for lower frequencies), correlated, and orthogonal THz channels (\(4\!\times \!4\)  SA-channel at \([300]{GHz}\)  using TeraMIMO [1]}). THz channels can be made orthogonal by careful spatial tuning of SA positions as described in [2]}. Due to high path loss, inter-cell interference has a negligible effect in the THz band compared to the lower frequencies and can be safely ignored. For MU-LP, we apply ZFBF to mitigate intra-cluster interference in both users. ZFBF is accompanied with rate-maximization to obtain the strong-user power matrix in NOMA (no interference following SIC). Fig. REF  verifies that MU-LP achieves a higher multiplexing gain (slope of sum-rate) in Gaussian and orthogonal THz channels. However, this observation does not apply to naturally occurring THz correlated channels. Applying ZFBF on ill-conditioned channels to cancel the interfering-user signal corrupts the main signal of the intended user, reducing the achievable rate. Therefore, ZFBF-based MU-LP is not a valid solution at the THz-band, despite its favorable low complexity.
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